It is well known that certain characteristics of some materials can be enhanced by reinforcing those materials with a suitably configured structure formed from a different material. In a typical example, the strength characteristics of one material can be enhanced by reinforcing that material with fibres of a different suitably strong material.
In the field of ceramics it is frequently desirable to reinforce a ceramic matrix material with high strength fibres of, for instance, alumina or silicon carbide. Difficulties arise, however, in ensuring that the reinforcing fibres are completely infiltrated by the ceramic matrix material.
One method of infiltrating reinforcing fibres with a ceramic matrix material is by the use of chemical vapour infiltration. In that technique the fibres are placed in an atmosphere of a suitable vapour which is caused to chemically break down to deposit a ceramic material on the fibres. Ceramics such as silicon carbide can be deposited in this way. However it is a slow process which is expensive to carry out. In addition-it does have a tendency to produce a matrix material which has some degree of undesirable porosity.
Another technique is one which utilises liquid phase reaction. This involves infiltrating the reinforcing fibres with a liquid which progressively oxidises or reacts with a gaseous atmosphere to form a ceramic matrix material. For instance, the fibres could be infiltrated by molten aluminium which is caused to oxidise to alumina as it infiltrates.
The drawback with this technique is that there is only a small range of materials which are suitable for use with it. Additionally there is the danger that unreacted metal could be left in the matrix material. Additionally the matrix material does tend to exhibit a certain degree of porosity.
A still further technique is one in which the reinforcing fibres are infiltrated with a liquid glass precursor material which is subsequently crystallised to form a ceramic product.
The difficulty with this technique is that:of the limited range of glass precursor materials which are available